The present invention relates to a joint structure for a tube support plate and a tube suitably applied to a dust-collecting apparatus for a hot gas, a heat exchanger for a hot gas and so on.
As a way for connecting in a gastight manner a metallic heat exchanger tube and a tube support plate in a heat exchanger, there has been known the way of welding both members or the way of expanding the heat exchanger tube.
In the joint structure formed by welding the tube support plate and the metallic heat exchanger tube, however, there have been problems that the metallic heat exchanger tube has insufficient heat resisting and corrosion resisting properties so that it is difficult to treat gas of any high temperature range, and a joint portion formed by welding may be damaged due to stress caused by difference in thermal expansion.
Various kinds of metallic bellows have been used as means for absorbing expansion and contraction caused by difference in thermal expansion, while assuring gastight sealing in a case that a metallic heat exchanger tube is connected to a metallic tube support plate. Namely, one end of the bellows is connected to the metallic tube support plate, and the other end is connected to the metallic heat exchanger tube by welding respectively. However, when a ceramic heat exchanger tube is used instead of the metallic tube, and gas having higher temperature than that of an ordinarily used hot gas is to be treated, it is impossible to use the bellows owing to its limited heat resisting properties. Further, it is difficult in practise to weld-joint the bellows to the ceramic heat exchanger tube. It is also difficult to directly weld-joint or bond the ceramic tube to the metallic tube support plate. Even if it is possible, the joint portion between the ceramic tube and the tube support plate, or the ceramic tube itself is broken by a thermal stress acting on the both members. Of course, it is impossible to employ a method of expanding a portion of the ceramic heat exchanger tube.
The inventors of the present invention have proposed in Japanese Unexamined Patent Publication No. 210489/1983 a joint structure attained by using combination of a resilient material such as ceramic cloth and fine particles such as silica sand, as a joint structure for jointing the ceramic heat exchanger tube with the tube support plate without suffering influence of thermal expansion. Although the proposed joint structure was effective, there were disadvantages in that when the number of sliding movements due to repeated thermal expansion and thermal contraction is large, the fine particles fall to thereby impair sealing properties, and the direction of the heat exchanger tube is limited to the vertical direction.